JAEA-Data-Code-2011-025

JAEA-Data/Code 2011-025

JENDL FP Decay Data File 2011 and

Fission Yields Data File 2011

Jun-ichi KATAKURA

Division of Nuclear Data and Reactor Engineering,

Nuclear Science and Engineering Directorate,

Japan Atomic Energy Agency

Tokai-mura,Naka-gun,Ibaraki-ken

(Received December 20, 2011)

The decay and fission yield data of fission products were compiled as JENDL FP Decay Data File 2011 (JENDL/FPD-2011) and JENDL FP Fission Yields Data File 2011 (JENDL/FPY-2011). After the release of JENDL FP Decay Data File 2000 (JENDL/FPD-2000) in 2000, new measured data have been accumulated and new TAGS (Total Absorption Gamma-ray Spectroscopy) data have been published. This new release is to reflect such new measured and available data. The file contains the decay data of 1284 FP nuclides (of which 142 nuclides are stable). In the compilation of the decay data, data of some nuclides were newly added and those of some nuclides were deleted. In order to keep the consistency between the number of nuclides contained of the decay data file and fission yields file, the JENDL/FPY-2011 file was also compiled.

The decay heat calculation for various kinds of fissioning nuclides were performed to confirm the validity of the JENDL/FPD-2011 and JENDL/FPY-2011 files. The calculated results were compared with the measured data and showed good agreement.The uncertainty analyses of the decay heat calculation were carried out by the method of sensitivity analysis. It was shown that the uncertainty was about 10 % at 0.1 s after a burst fission.

Keywords: Decay Data, Fission Yields Data, Fission Products, JENDL, Decay Heat, Sensitivity Analysis

JAEA-Data/Code 2011-025

2011 JENDL FP

片倉　純一

(2011 12 20 )

FP JENDL FP Decay Data File

2011 JENDL/FPD-2011 JENDL FP Fission Yields Data File 2011 JENDL/FPY-2011

2000 JENDL FP Decay Data File 2000 JENDL/FPD-2000

TAGS (

1284 FP 142

求め、瞬時照射後0.1 10 %

319-1195 2–4

JAEA-Data/Code 2011-025

Contents

3.3Summary Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.1Data Format of Yield File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2Example of Fission Yield Data in JENDL/FPY-2011 . . . . . . . . . . . . . . . . . . . . . . . . 52

5 Fission Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6 Decay Heat Calculations and Their Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7Comparisons between Calculated Results and Measured Data . . . . . . . . . . . . . . . . . . . . 5960

7.1 235U Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7.2239Pu Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.3 238U Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.4241Pu Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.5232Th Fission and 233U Fission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

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3. . . . . . . . . . . . . . . . . . . . . . . . . 4

3.3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2 JENDL/FPY-2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6059

7.1 235U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7.2239Pu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.3 238U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.4241Pu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.5 232Th 233U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

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1Introduction

The decay data and fission yields data of fission products (FP) are important for the analysis of the reactor decay heat and the radioactive inventory of the fission products in nuclear reactors. The accuracy of such calculation as the decay heat depends on the adopted data. Although there are about 1000 FP nuclides produced after fission, their decay data are not always reliable ones. Roughly speaking, about a half of them has no measured or poorly measured decay data because of the difficulty to obtain experimentally the data with short half-lives. It is not suitable to use such deficient decay data for decay heat calculation at short cooling times after fission when the nuclides with short half-lives mainly contribute to the decay heat. Then it is necessary to compensate such deficient decay data with some other data.

Japanese nuclear data committee (JNDC) has a long history to develop the nuclear data file for decay heat calculation 1). They adopted theoretical decay data, especially, decay energy values for the nuclides with deficient decay data and succeeded to show good agreement between the calculated decay heat values and measured ones. The JNDC nuclear data libraries which adopted the theoretically calculated decay energy were developed for the decay heat calculation. The libraries, however, had different format from that of the JENDL, Japanese nuclear data library, format, that is, ENDF-6 format 2). In order to include the decay data into the JENDL family, JENDL FP Decay Data File 2000 3) (JENDL/FPD-2000) with ENDF-6 format was developed and released in 2000.

It has passed more than 10 years after the release of the JENDL/FPD-2000 file and new measured decay data have been accumulated during the period. In the measurement field, the activity employing TAGS (Total Absorption Gamma-ray Spectroscopy) method was initiated by international cooperation with the aid by IAEA NDS (Nuclear Data Section) and OECD/NEA WPEC (Working Party on International Evaluation Cooperation) 4)and the measured decay energy data of some FPs are available now 5). The application of TAGS method to obtain beta strength function were performed at first in ’70s 6) and extensively studied by a group at Idaho National Laboratory 7). Although the usefulness of such TAGS data for the decay heat calculation was fully recognized, it was rather difficult to get consistent data between the decay energy values and their spectra to suit to the evaluated data format and the TAGS data were not included in the JENDL/FPD-2000 file. When we revise the JENDL/FPD-2000 file, however, it is decided to try to include the new TAGS data with spectral data.

Using new measured decay data including the TAGS ones, JENDL FP Decay Data File 2011 (JENDL/FPD2011) was compiled. In the compilation process, it was considered that the good prediction ability of the JENDL/FPD2000 file should be kept even if the newly measured decay data replaced the old ones.

The fission yields data were also revised because of the increase of the number of the nuclides contained in the JENDL/FPD-2011 file. As the number of the nuclides in the yields data file needs the consistency with that in the decay data file when they are used for the decay heat or the inventory calculation, the nuclides contained in the fission yields file were selected to keep the consistency of the number of the nuclides with that of the JENDL/FPD2011 file. Then the fission yields file JENDL FP Yields File 2011 (JENDL/FPY-2011) were compiled.

In order to confirm the applicability of the JENDL/FPD-2011 and JENDL/FPY-2011 files, the decay heat calculation using them were performed and compared with measured decay heat data of various kinds of fissioning nuclides. In the calculation, the uncertainties of the calculated results were derived by sensitivity analyses.

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2Decay Data

The JENDL/FPD-2011 file includes the decay data of 1284 fission product nuclides from A = 66 to 172. Out of them 142 nuclides are stable ones. So there are 1142 unstable nuclides in the file. As the JENDL/FPD-2000 file contains the data of 1087 unstable nuclides (1229 including stable ones), the newly added data are for at least 55 nuclides. After the compilation of the JENDL/FPD-2000 file, many isomeric states have been identified and some in the JENDL/FPD-2000 file have been rejected by experiments.

The primary data source of the decay data is the ENSDF 8) (Evaluated Nuclear Structure Data File), which has been prepared under the international cooperation. The newer data than those in the JENDL/FPD-2000 file are taken from the ENSDF file as of October 2010.

The number of the nuclides in the file is summarized in Table 2.1. The continuous spectra of gammaand beta-rays in Table 2.1 are theoretically calculated ones. And they are used to compensate incomplete measured spectral data and theoretical decay energy values or TAGS ones are adopted to those nuclides. There are 7 newly measured TAGS data. They are adopted in the JENDL/FPD-2011 file. Since the TAGS data give beta strength function, the beta-ray spectrum can be obtained from it if the beta decay forbiddenness is suitably assumed. The gamma-ray spectrum, however, can not be obtained from the strength function. Theoretically calculated gammaray spectra were used to compensate the spectroscopically measured ones of the nuclides with the TAGS data. Then the theoretical decay energy values are adopted to 502 (=509-7) nuclides in gamma-ray energy and to 486 nuclides in beta-ray energy.

Table 2.1 Number of nuclides of various types

JENDL/FPD-2000 in parentheses

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2.1Decay Energy and Spectra

The decay data in the ENSDF file as of October 2010 were converted from the ENSDF format to the ENDF format by RADLST code 9) which can be downloaded from National Nuclear Data Center, Brookhaven National Laboratory, USA. The data in the ENSDF file, however, are summarized with the level property of a daughter nuclide. When there are two more daughter nuclides, they are provided in different data sets. For example, in the case of 86Rb decay, there are 2 decay modes, that is, β− and electron capture decays. The β− decay produces 86Sr as its daughter nuclide. On the other hand, the electron capture decay yields 86Kr nuclides. The former is in the

86Sr data set and the latter in 86Kr one. As the data in the ENDF format, however, are arranged in the property of a parent nuclide, the both data sets have to be merged into one data group of the parent nuclide 86Rb.

And also when a daughter nuclide has an isomeric state, it sometimes happens that the radiations from the isomeric state to the ground state are included in the parent nuclide radiations. This situation brings about the double counting of the radiations as long as the meta stable state is considered as a different nuclide. In order to avoid such double counting, the radiations from the isomeric state have to be removed from those of the parent nuclide.

Although the data in the ENSDF file are provided through detailed examination by evaluators as most probable ones, the data often suffer from the so-called “Pandemonium Problem” 10). When Q value of a FP nuclide increases, more higher-lying levels in the daughter nuclide can be populated with less intense gamma-rays. The weaker gamma-rays are not always observed in a usual β − γ spectroscopy method. Since the level scheme constructed without many unobserved weak gamma-rays is incomplete, it gives a lower average gamma energy and a higher average beta energy than the true average energy values. It is not suitable to adopt the average energy values derived from such incomplete decay scheme. In order to avoid such situation, the JENDL/FPD-2000 file adopted theoretically estimated average decay energy values and they were successfully able to reproduce the measured decay heat values for various kinds of fissioning nuclides.

In the compilation of the JENDL/FPD-2011 file, the theoretical values are also adopted for the nuclides with incomplete decay scheme excepting those with the TAGS data. As it is rather difficult to determine the nuclides with incomplete decay scheme, the adoption of the JENDL/FPD-2000 file was consulted. If the highest level energy observed is low enough comparing the Q value and the average decay energy value is much lower than that of the theoretical one, the measured data are not adopted in the JENDL/FPD-2011 file.

In the case of the adoption of TAGS data, the beta-ray spectrum was calculated from the beta strength functions obtained by the TAGS method assuming allowed transition when the beta decay forbideness was not known. In order to keep the consistency between the spectrum and the average decay energy, the beta decay energy calculated from the spectrum was adopted in the JENDL/FPD-2011, which was a little bit different from the reported decay energy value. For the gamma-ray energy, the reported values of the TAGS data were adopted and theoretically estimated spectra were used to compensate the difference between the TAGS data and the spectroscopic one.

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2.2Delayed Neutron Branching Ratio

The delayed-neutron branching ratios were also revised based on the ENSDF data and the compilation by Pfeiffer, Kratz and Moller¨ 11), although the spectral data of the delayed neutrons were not included in the JENDL/FPD-2011 file. When the ENSDF file does not contain the delayed-neutron branching, the calculated branching ratios of the empirical Kratz-Herrmann formula by Pfeiffer et al. were adopted.

3Data Format and Summary Data Table of Decay Data File

3.1Data Formats

The decay data have been compiled in the format of ENDF-6. The format is reported in the reference and briefly described here. Each datum in the file is stored in a 80 columns record and each record contains three identification numbers: MAT, MF and MT. The MAT number is a material number which is uniquely assigned to each nuclide. The MF number is a file number. The file 1, MF=1, contains the comments on the data included. The radioactive decay data are included in FILE 8, that is, MF=8. The MT number shows a reaction numbers in the ENDF-6 format. The number of MT=457, however, is assigned to radioactive decay data. Each decay datum, therefore, has the identification numbers of MF=8 and MT=457. The structure of the decay data file in the ENDF-6 format is shown in Table 3.1.

The meaning of the variables in Table 3.1 is following: